The present invention relates generally to the concept of dimensional weighing to determine the charge required by a carrier for transporting a package or parcel, and more particularly to a dimensional weighing system suitable for use by a variety of shippers and carriers to determine accurate freight charges for packages or parcels that are considerably oversized in comparison to their actual weight.
A detailed description of the background and development of the concept of dimensional weighing, as well as the significant problems and disadvantages of prior art dimensional weighing systems, is set forth in the Background of the Invention portion of the specification in the above cross-referenced application, which is hereby incorporated herein by reference.
Briefly, the invention disclosed and claimed in that application is a dimensional weighing system in which a measuring frame having three measuring arms which extend from a common juncture along the three axes of cartons which must be measured to determine the volume thereof is mounted in operative association with the platform of a weighing scale on which the cartons are placed in a predetermined position. A plurality of optical emitters, such as LEDs, are evenly positioned along the length of the measuring arms, and either one or three optical sensors, depending on the particular embodiment of the invention, are positioned such that the sensor(s) respond to all emitters on the measuring arms that are not obscured by the parcel. A computer processing means receives and stores the length, width and height linear dimensions of a carton from the optical sensors and calculates its volume. The computer then compares that volume with a predetermined threshold volume stored in a memory, so as to determine, firstly, whether the volume of the carton is less than the predetermined threshold volume so that it can be shipped at a shipping charge based on the actual weight of the carton as determined by a suitable weighing scale, or is larger than the predetermined threshold volume and may therefore require that a dimensional weight be calculated on which a shipping charge is based. If the latter situation prevails, the computer processing means then compares the dimensional weight of the carton with the actual weight to determine which is larger to ensure than the shipping charge is based on the proper weight.
One problem which became evident with the dimensional weighing system described and claimed in the above cross-referenced application is that the optical measuring portion of the apparatus requires a substantially large volume of unobstructed space surrounding the package or parcel being measured because of the distance which the optical sensor or sensors, as the case may be, must be spaced from the measuring arms in order for the emitters not obscured by the carton being measured to be exposed to the sensors and not lie in a "shadow" of the carton relative to the location of the sensor(s). Thus, with respect to the embodiment utilizing only one sensor, this required that the sensor be located at or near to the diagonally opposite corner of the package, i.e., as far out horizontally from the juncture of the measuring arms as the length of these arms, and as far up vertically from the juncture of the measuring arms as the height of the vertical measuring arm. With respect to the embodiment utilizing three sensors, the sensor for the vertical measurement along the vertical arms must still be in the same location as that just described for a single sensor, and the sensors for the two horizontal measuring arms must be located in the same plane as the measuring arms and as far out from the free end of each measuring arm as the length thereof.
In either of the foregoing situations, the problem that arose was that it was often difficult for an operator to place a carton on the platform of the weighing scale, especially if the size of the carton approximated that of the full length of the measuring arms, because of the presence of the first mentioned sensor located adjacent to the diagonally opposite corner of the carton from the juncture of the measuring arms. Depending on the size of the carton, the presence of the sensor in this location made it very awkward or cumbersome to position the carton on the scale platform without inadvertently striking the sensor or one of the horizontal meaning arms, or dropping the carton on the scale platform or inaccurately positioning it thereon. This problem was often further complicated by the presence of supporting structure for the sensor, regardless of whether the supporting structure for the sensor was mounted on the same base as the scale and measuring arms or was suspended from above, either of which only made positioning the carton more difficult. In the situation where there are three sensors, there is the added problem of ensuring that there is nothing lying in the plane of the horizontal measuring arms that might obstruct emitters beyond the dimensions of the carton from the two sensors measuring along the horizontal measuring arms, such as, for example, the operator's hands or arms.
In view of the fact that the speed with which an operator can dimensionally weigh successive packages or cartons with the dimensional weighing apparatus is a significant factor in ensuring that the apparatus is economically viable, it becomes extremely important to enable the operator to place packages or cartons on the weighing scale platform, and remove them therefrom, as rapidly and as accurately as possible, so as to maintain a high through put rate and do so without risk of damage to the apparatus which could lead to down time to allow for necessary repairs.
Another problem which became evident with the invention disclosed in the above cross-referenced application was that the cost of the apparatus was relatively high because of the need for a large number of LED emitters that were required to obtain a high degree of accuracy in measuring the linear dimensions of packages and cartons. The resolution of the measuring apparatus depends on the spacing of the emitters, and the closer together the emitters are placed along the measuring arms, the more accurate the measurements will be. Thus, to determine an accurate volume for a carton it may be necessary to provide emitters along the measuring arms that are only one quarter to one half inch apart. Further, a large number of emitters requires more complex computer control components, which further adds to the cost.
Still another problem which became evident with the previous invention was that it did not have the capability of providing a preliminary indication of whether or not it was necessary to dimensionally weigh a carton based on a rough calculation of the volume of the carton, a feature which could greatly reduce the cost of the dimensional weighing apparatus. It has been found from experience that only about 20% of the packages and parcels handled by a carrier in a given period of time actually require dimensional weighing in order to determine a proper shipping charge based on a dimensional weight, whereas a proper shipping charge can be based on the actual weight of the packages and parcels for the other 80%. This presents the problem that, not only is the dimensional weighing apparatus relatively expensive in the first place, but also it is effectively utilized for only about 20% of the packages and parcels being shipped. Thus, while the apparatus of the prior invention may be cost effective for a large carrier or shipper, e.g., UPS, Federal Express, etc., or catalog merchandise mail order businesses, it is often not cost effective for small to medium carriers or shippers.
Thus, there is a need for a dimensional weighing apparatus which is sufficiently economical to be cost effective for small to medium size carriers and shippers and yet which provides sufficient accuracy in determining the volume of a carton that the degree of error from making rough calculations is economically acceptable. Also, it is desirable that a low cost dimensional weighing apparatus ideally suited to small and medium volume shippers have the capability of providing a preliminary indication of whether it is necessary to dimensionally weigh a particular carton based on a rough calculation of the its volume, so that the operator then has a choice of permitting the dimensional weighing apparatus to calculate a rough shipping weight on which the shipping system will calculate the shipping charge, or of manually taking accurate measurements of the carton to accurately determine a dimensional shipping weight on which an accurate shipping charge can be calculated.